1. Field of the Invention
The invention relates to a process for producing doped semiconductor wafers from silicon, which contain an electrically active dopant such as boron, phosphorus, arsenic or antimony, if appropriate are additionally doped with germanium, and which have a defined thermal conductivity. The invention also relates to semiconductor wafers formed from silicon, which are doped with germanium in a concentration of up to 2·1020 atoms/cm3 and with an electrically active dopant, and which have specific properties with regard to thermal conductivity (TC) and resistivity (R).
2. Background Art
It is fundamentally advantageous if the semiconductor wafer, as a base material (substrate) for electronic components, is supplied with defined physical properties when possible. Ideally, a substrate should have only slight fluctuations in all principle parameters both within a single wafer and between different wafers of the same specification. The thermal conductivity of substrates is one such crucial property which is of great importance to process management in the fabrication of electronic components and with regard to the properties of the finished products. For example, the thermal conductivity of semiconductor wafers formed from silicon plays a crucial role in determining the properties of these wafers during processing to form electronic components and the possible range of uses for the finished component. Consequently, substrates with a well-defined and uniform thermal conductivity are desirable.
However, the thermal conductivity of semiconductor wafers formed from silicon is complex and expensive to measure, and consequently this parameter is not measured in standard production. Thermal conductivity is composed of a phononic component and an electronic component. Both contributions are important in single-crystal silicon at room temperature. The electronic component of the thermal conductivity is substantially proportional to the electrical conductivity of the substrate, while the phononic component is related to the distribution of the atomic masses in the solid state. It is known that pure-isotope silicon has a particularly high thermal conductivity, whereas doping elements lower the thermal conductivity.